IPA: /ˈtruːpər/
KK: /ˈtruːpər/
A person who is a member of a military unit, especially in the cavalry or police force.
The trooper patrolled the area on horseback, ensuring safety and order.
Trooper originates from the word 'troop' (from Old French *troupe*, meaning a group or crowd) combined with the suffix '-er' (meaning a person who). A trooper is a person who is part of a group, especially in a military context.
Think of a 'group' ('troop') of people, and the '-er' indicates a person. A trooper is someone who belongs to that group.